Device for the correction of spinal deformities

ABSTRACT

The device consists of at least two segments which are fixed on spinal vertebrae and which are mutually interconnected. Each segment (1) is fixed on at least one vertebra (7) by means of at least one fixing segment (3). Each segment (1) is connected by means of at least one spring (4) by the force coupling with at least one other segment (1&#39;) fixed on at least one other vertebra (7&#39;). The connecting line of 8 the spring (4) ends contains with the vertical vertebral axis (7) an angle to 45° in the frontal as well as in the sagittal plane in the ventral and/or dorsal direction. Required stability of the spine is ensured while preserving the necessary flexibility and adaptation to growth.

This application is filed under 35 U.S.C. 371 based on PCT/SK96/00003,filed Mar. 27, 1996.

TECHNICAL FIELD

The invention relates to the device for the correction of spinaldeformities based on metal implants applied by an operation.

BACKGROUND ART

Under the term of the spine deformity are herein understood scolioses(abnormal curvatures of the spine in the sagital plane) and pathologicalkyphoses and lordoses (abnormal curvatures in the sagital plane). Theoperative correction of spine deformities by means of metal implantsmade of special stainless biocompatible steels and titanium alloys,represents the most effective manner of medical treatment of spinedeformities and at the same time, a medico-technical problem which isbeing actual practically already one century, and which still has notbeen solved with satisfaction. Actually are known several principalconstructive solutions for implants to treat spine deformities but eachof them has, in addition to certain advantages, also a series ofinsufficiences. The whole set of known solutions may be divided intothree basic groups which may be characterized in the following manner.

The first group represents a set of solutions which may be characterizedas rigid systems. A significant feature of these systems is that theycontain at least one rod or a plate which is introduced by an operationon the place of a spine deformity, almost in parallel with the spine,while in its whole lenght it is connected with at least two spinalvertebrae by various shaped fixing elements (hooks, clamps, screws, wireknots, etc) installed on it which are fixed on the body or the processusor the laminae of vertebrae. Usually two rods are used which aremutually in at least two spots interconnected and operationallyinstalled along the sides of the spine while several or all vertebraeare then connected with them in its deformity place. From the functionalpoint of view occurs the correction of the deformity by acting,regarding the long spinal axis, of cross tensile and/or pressure forceson deformed vertebrae while is made use of the rigidity of the rod orrods. These systems usually well correct and also stabilize the spine inall three planes but they do not allow the motion and the growth ofstabilized segments. Therefore, when applying them, the joints areabolished by an operation and by putting on bone grafts will be evokedthat the spine will grow together (spondylodesis, fusion) in thedeformity place and that will locally prevent its growth and themobility will be annulled. Presently, it is possible to insert here asrepresentatives, for instance, of the Wisconsin instrumentationsDrummond D. S., J. Pediatr. Orthop., 4,1984, 397-404; Drummond D. S.,The Orthop. Clin. of North Am., 2, 1988, 208-289!, Cotrel-DuboussetCotrel Y., Dubousset J., Rev. Chir. Orthop., 70, 1984, 489-495; CotrelY., Dubousset J., Orthop. Trans., 9, 1985, 118!, TSRH, the Isola systemusing the rod combined with the plate Asher M. A. et al.: Isola SpineImplant System: Principles and Practice, acroMed, Cleveland, 1991!,Central-Stab-System, the Luque instrumentation Luque E. R., Cardoso A.,Orthop. Trans., 1, 1977, 136; Luque E. R.: Tailoring Surgery to SpinalPathology. In Segmental Spinal Instrumentation. Thorofare, N.J., SlackCo., 1984! and others. This group may include also internal fixators(e.g. Socon (Socon-Fixateur Interne-Aesculap, Prospekt N. C-627 1091(3,Germany), Kluger's fixator DE P321957.3; Dick W. et al., Paraplegia, 23,1985, 225-232!, Matzen's fixator Internal Fixator for the Lumbar Spineacc. to Matzen, Ulrich, Dr. HS (de Apr. 16, 1992 derer/e-matzen.pm.3!and others).

The second group is represented by systems which may be characterized assemirigid ones. For these instrumentations is typical that, they aremade of:

a) The rod equipped at least at its ends with appropriately shapedfixing elements, which is by an operation applied from the concave orconvex side of the deformity, and the fixing elements are fixed, underthe actual maximum possible straightness of the spine deformity, onvertebrae in the area of the beginning and the end of a deformity, whilefrom the functional point of view the correction of a deformity occursby acting parallel expanding forces with the long spinal axis on itsconcave side or by acting pressing forces on its convex side;

b) The wind spring equipped at its ends with appropriate fixing elementsand which is applied by an operation from the convex side of thedeformity, and the fixing elements are at actual tension of the springfixed on vertebrae in the area of the beginning and the end of thedeformity while from the functional point of view the correction of thedeformity occurs by acting parallel forces with the long spinal axis onits convex side,

c) From the combination of elements according to both previous pointswhich may be also mutually interconnected while from the functionalpoint of view the correction of the spinal deformity occurs by actingparallel compressing forces on its convex side and simultaneously byacting parallel distracting forces on its concave side.

Instrumentations belonging to the group of semirigid systemsappropriately correct the spinal deformities and significantly or fullyrestrict the motion within the area of the spinal deformity only in thedirection of acting correction forces. The spine is never corrected inall three planes (therefore, at their application the external fixationby the corset or jacket is always inevitable), but the instrumentationsrestrict the growth of the spine for at their application the joins areabolished by an operation and the spondylodesis is evoked. This groupinclude, for instance, Allan's Allan F. G., J. Bone Joint Surgeon, 37(B,1955, 92-96! and Kazmin's distractor, spiral springs according to GrucaGruca A., Beitr. Orthop. u. Traumal., 5, 1958, 1-11; Gruca A., J. BoneJoint Surg., 40(A, 1958, 570-584!, their modification according to WeissWeiss M., Bentkowsky Z., Clin. Orthop., 1974, 103-109!, Harrington'sdistraction and compression system Harrington P. R., J. Bone JointSurg., 44(A, 1962, 591-610; Harrington P. R., Orthop. Clin. of NorthAm., 3, 1972, 49-67!, and others.

The third group may be characterized as telescopic systems which arecharacterized by the fact that they consist of:

a) The rod of a constant lenght on which are fixed appropriate fixingelements so that the position of at least one element is adjustable inthe long spinal axis direction.

b) Two rods (the telescopic rod is made as a rod inserted by one its endinto the coaxial tube) mutually interconnected on both ends, with fixingelements usually situated at the ends of rods, while the length of rods,and thus also the position of at least one fixing elements, isadjustable in the long spinal axis direction.

The mentioned instrumentations are applied by an operation along thesides of the spinal deformity and through its fixing elements ensure thetransfer of correcting forces on deformed spinal vertebrae. With theinstrumentation according to the point a) it is possible, atperiodically repeated operative interventions of a local scope, tochange every time the position of at least one fixing element so thatthis position be brought into harmony with the growth of the spine. Theinstrumentation according to the point b) is spontaneously modified inthe length in accordance with the growth of the spine. A significantdisadvantage of these instrumentations is the minimalization of thescope of unevitable changes on the spine and the use of one and onlyonce applied instrumentation by an operation for the period of thespinal growth. But, they have still a disadvantage characteristic forall the other, till now not mentioned solutions, i.e. significantrestrictions of the spinal mobility. This group may actually includeHarrington's distraction instrumentation Moe J. H., Orthop. Clin. ofNorth Am., 3, 1972, 17-48! using a ratchet or threaded rods which doesnot assure the rotational stability, and therefore the external fixationof the spine by a corset or jacket is unevitable. The last system isUlmer-Teleskop-Stab instrumentation used with the neuromuscularscolioses which stabilizes the spine in all three planes (the need offixation by the corset or jacket is therefore not required), it correctsthe deformity and at the same time, it follows telescopically its growthin the direction of its long axis.

From the above-mentioned facts it in obvious that all till present knownsolutions of devices for correcting spinal deformities have twosignificant disadvantages:

1) A significant restriction, respectively, the total liquidation of themobility and growth of the spine at minimum in the area of itsdeformity,

2) The need to perform multiple operative interventions at theirapplication on the growing spine what means a great load for thepatient's organism.

The aim of the submitted invention is to provide the medical practicesuch an instrumentation which will suppress these insufficiences to amaximum possible extent or which will fully eliminate them.

DISCLOSURE OF INVENTION

The device for correcting the spinal deformities according to theinvention consists of at least two segments which are fixed on thespinal vertebrae and which are mutually interconnected while theprinciple of the invention is that each segment consists of the segmentbody connected with at least one fixing element (e.g. in the form of thehooks, clamps, screws, wire knots, etc.), by which the segment is fixedon at least one spinal vertebra in the area of its deformity and at thesame time, it contains at least one spring the length of which issignificatly greater than its other dimensions and by means of which isconnected through the power coupling with at least one other segmentfixed on at least one other spinal vertebra. Moreover, the line goingthrough the beginning and the end of the spring forms an angle to 45°with the vertical vertebral axis in the frontal as well as in thesagital plane, in the ventral and/or dorsal direction.

The solution according to the invention may include two basicalternatives of fixing the spring. In the first case each end of thespring is firmly fixed (for instance, in such a manner that it is madeas an integral part of the segment body or it is fixed on it by theweld, screw joint, etc.) on another segment and thus forms the bridgingbetween them which provides the force transfer from one segment toanther. In the second case one end of the spring is firmly fixed on onesegment and the second segment is equipped with the bearing case in theform of the depression or in the form of the aperture in the body ofanother segment, in which the second end of the spring is stored. Thebearing case when applying the device according to the invention,insulates the contacting spot of the spring with the segment fromsurrounding tissues and thus prevents their damage when moving the freeend of the springy element due to the flexion of the spine. The bearingcase has principally a form of the ring or a part of the ring with acircular, elliptical or rectangular aperture, respectively, with acircular, elliptical or rectangular aperture, created in the segmentbody while the cross dimensions of the aperture are at least by 0.01 mmgreater than the corresponding dimensions of the springy element freeend.

From the production as well as application point of view it isconvenient if the segments are unified, i.e., if every segment containsan springy element fixed on it and a bearing case as well. When applyingthe segments on a spinal deformity is required that the forces actingthrough segments on individual vertebrae have a differenciated size,i.e. that the springs fixed on separate segments have differenciatedmechanical features. It may be conveniently achieved in such a mannerthat individual springs are made from a different material and/or theyhave different cross sections in respect to their longitudinal axesand/or they differ in shape and/or they are fixed on separate segmentsin different positions, from the point of view of the their fixationplace on the segment as well as of their slope regarding the vertebralvertical axis.

From the point of view of the unification required at the production ofsegments and the simplicity of their application on the spine is veryimportant if a prominence is formed on the segment body in the shape ofa globular section in which at its top an aperture with the thread iscreated and the end of the spring is also shaped in the form of a followglobe section having the internal diameter principally equalling to thementioned prominence radius, but having the height legs by at least 0.01mm, and in which at its top is created a through circular aperture. Inaddition to it, the segment contains also a fixation washer with theexcavation in the shape of a globular aperture having the diameterprincipally equal to the external radius of the mentioned end of thespring and near the top of the mentioned excavation is formed a circularaperture, while the mentioned spring end is a concave side placed on thementioned prominence and on its convex side is located the mentionedexcavation of the fixation washer. The mutual position of these elementsis fixed by a screw having the diameter less by at least 0.01 mm thanthe diameter of apertures in the spring and in the fixation washerthrough which it passes and which is tightened in the thread found nearthe top of the mentioned prominence on the segment body. The principaladvantage of such a construction of the segment is that with a minimumvariety of shapes of springs and segments, relative simplicity of theirshapes and production and a simple assembly at their application on aspinal vertebra, respectively, vertebrae, it is possible by means of asimple change in turning the spring, within the scope of angles,determined by characteristics of a given deformity and a concretesegment production (mainly related to the mutual ratio of the screwdiameter and the aperture size at the end of the spring), to reach alarge variety of force acting between separate segments.

In cases, when for the correction of an expressive spinal deformity isrequired to form a strong force coupling between segments, mainly in thedorsal direction, that there is a real danger of damaging this part of aspinal vertebra on which the segments are fixed, it is extremelyimportant if the segment is made principally in such a manner asdescribed above, but with the difference that in a given sphericalprominence on the segment body is created a through aperture leading toat its top. Through this aperture passes a hollow screw which istightened in a vertebra, most conveniently, through the pedicle in thespinal vertebra body, and in this screw is an aperture with the threadto fix the screw fixing a mutual position of separate parts of thesegment. By means of such a constructive solution it is possible torather better distribute the force load acting on the vertebra in theplace of fixing the segment and thus significantly reducing thepossibility of its damage.

For both last mentioned alternatives of the constructive execution ofthe segment it is convenient if the later contains the bearing case inthe form from one side open excavation created in the segment body whilethis bearing case is covered by the fixation washer from its open side.This helps to reach a full insulation of the spring end from the tissuesin its surrounding and at the same time, it will significantlysimplifies the segment application on spinal vertebrae since after theinstallation of the first segment with a spring it is possible, withouta force coupling, to instal the second segment and the force couplingbetween the mentioned segments will be formed by an additional insertionof the spring end into the bearing case while its position in the caseis fixed by the fixation washer of the second segment as well as by thefixation of its own spring.

While the spring is fixed only on one segment and its free end isinserted into the bearing case of the following segment, due to thelimited length of this case there is a real danger that a very bigflexion of the spine may evoke the release of the spring free and fromthe bearing case and the consequent serious damage of surroundingtissues, leading to the necessity of a futher operative intervention.The mentioned danger is eliminated by such a construction of the springand the bearing case according to the invention, in which the springcontains at its free end at least on a part of its circumference theenlargement, and at the end of the bearing case remoted from thesegment, on which the mentioned spring is fixed, on a part of its lengthis formed a groove into which the free end of the spring will fall atthe excessive flexion of the spine. The mentioned groove in the bearingcase is approprietary made in such a manner that it allows within agiven scope not only the straight-lined notion but also the rotationalmotion of the spring in the bearing case.

From the point of view of applying the segment on a spinal vertebra itis convenient if the segment contains a fixing element in the form of ashaped clamp equipped at the ends of arms with a fixation screw whichallows, when applying the segment on a vertebra, to tightened togetherthe ends of the shaped clamp arms. The aperture in the shaped clampcorresponds to the arch shape of the spinal vertebra on which thesegment will be fixed, it conveniently has a shape of the cross cut ofthe vertebral arch in the place between the spinous processus and thepedicle of the vertebra.

The device for the correction of spinal deformities according to theinvention has, in addition to all already mentioned advantages comparedwith solutions according to the state of technics a very significantadvantage that due to the springy interconnection of its individualsegments it allows the patient flexions of the spine in a scope requiredfor the normal life and also during the intensive growth of the spinewhich it does not restrict, and at the same time, the force couplingbetween segments is so firm that any orthosis is needed. The submittedsolution is so constructively as well as applicably flexible and it maybe very simply modified to a concrete kind of the spinal deformity anddue to the limited number of required operative interventions (usuallyone or two operations will be sufficient) it represents for the organismof the patient a minimum load at shortening the time for the operationand decreasing the blood losses.

BRIEF DESCRIPTION OF DRAWINGS

For a better comprehension of the invention the solution is shown on theenclosed drawing where it represents:

FIG. 1 A schematic view on three segments situated on three spinalvertebrae.

FIG. 2 A view on two segments interconnected with one spring firmlyfixed on both segments.

FIG. 3 A schematic view on three segments with marked spinal vertebraeon which they are fixed.

FIG. 4 A view on a segment with a shaped clamp and a partial cut of thebearing case.

FIG. 5 A cross cut of the A--A segment according to the FIG. 4.

FIG. 6 A cross cut of the spring with a fixation washer and a screw.

FIG. 7 A cross cut of a segment fixed on the vertebra by a hollow screw.

MODES FOR CARRYING OUT THE INVENTION EXAMPLE 1

Segments 1, 1' and 1" according to the FIG. 1 are made of stainlesssteel according to the ISO 5832/211 while the segment 1 fixed on thevertebra 7 consists of the segment body 2 and a fixing element 3 made asa shaped clamp, the arms of which are mutually tightened together by atightening screw 6. An integral part of the segment body 2 is a spring4, the second end of which is located in a bearing case 5' of the nextsegment 1', which is made as a through aperture. The next segments 1',1" are equipped with identical fixing elements 3', 3" made as a shapedclamp while each of the mentioned segments 1, 1' is constructivelymodified for fixing on one spinal vertebra 7', 7". When applying thedevice for the correction of spinal deformities according to the FIG. 1the segment 1 is firstly fixed can the vertebra 7 by means of its fixingelement 3, at the end of its spring 4 is inserted the bearing case 5' ofthe segment 1' which is turned by appropriate instruments to a positionensuring the creation of a required force coupling between the segments1 and 1' and by means of its fixing element 1" is fixed on the spinalvertebra 7". The third segment 1" is fixed on the spinal vertebra 7" byits fixing element 3" and then by means of appropriate instruments isturned to a position required for the creation of necessary force actingon the segment 1', in this position the spring 4' will be transplacedthrough its bearing case 5" and its and is fixed on the segment 1' bythe screw 8'.

EXAMPLE 2

The segments 1, 1' according to the FIG. 2 are made of stainless steelaccording to the ISO 5832/211, while the segment 1 containts the fixingelement 3 made as a hook. In the body 2 of the segment 1 is inserted andby the screw 8 fixed the spring 4 the second end of which is firmlyfixed by the screw 8 in the bearing case 5' of the next segment 1',which is made as a through aperture. In the spring 4 is created at itsend a longitudinal aperture, through which passes the screw 8' and bymeans of which, during the growth of the spine may be modified thedistance between both mentioned segments. The second segment 1' isequipped with the fixing element 3' made as a groove on the surface ofthe fixing element 3' into which, when applying the segment on thespine, is inserted a wire knot fixing the element on a correspondingvertebra. Each of the mentioned segments 1, 1' is constructivelymodified for being fixed only on one spinal vertebra.

EXAMPLE 3

The device for correcting the spinal deformities according to the FIG. 3is made from the titanium alloy Ti--6Al--7Nb and consists of threesegments 1, 1', 1" from which only the first segment 1 is fixed on twospinal vertebrae 7, 7' by means of the shaped clamp 3 and the other arein the same way fixed always on one vertebra. On the segment 1 are fixedtwo springs 4.1, 4.2 from which the first spring 4.1 has long its entirelength a constant rectangular cut and is made of stainless steelaccording to the ISO 5832/1 and is fixed on the segment 1 by the screw 8while it goes through the bearing case 5', made as a rectangularexcavation in the second segment 1', and the bearing case 5.1" made alsoas a rectangular excavation in the third segment 1", in which the madegroove 17 prevents the declutching of the spring 4.1, equipped at oneend with the prominence 16 of the case 5.1". The second spring 4.2 is anintegral part of the segment 1, has along its entire length a constantcircular cut and is fixed with its second end in the second bearing case5.2" of the third segment 1", made as a through aperture of the circularcut.

EXAMPLE 4

A segment of the device for the correction of spinal deformitiesaccording to the FIG. 4 and consists of the fixing element 3 made as ashaped clamp and the body of the segment 2 on which the prominence 9 isformed in the shape of a globular section (see the cut A--A in the FIG.5) with the aperture 10 and the thread. On the prominence 9 is stored anequally shaped and 11 of the spring 4 with the through aperture 12 (formore details see the FIG. 6) and the fixation washer 13 is put on it,equipped with a semi-circular excavation 14 and a through aperture 15 atits top while the mutual position of the mentioned elements is fixed bythe screw 8, passing through the mentioned apertures 12, 15 and beingtightened in the aperture 10 having the thread. The bearing case 5 ismade as a from one side open excavation in the body 2 of the segment inwhich on one side, in about the mid of its length, a groove 17 is made.In the case 5 is located a free end of the spring 4', firmly fixed onthe not shown previous segment equipped at one end with the prominence16 which is situated in the groove 17. The position stability of one endof the spring 4' in the bearing case 5 is ensured by the fixation washer13 which loses the open side of the bearing case 5. The spring 4' isfixed on the previous not shown segment in such a position that underthe pressure it touches the body of thee segment 2 and pushes it to theposition ensuring the correction of a given spinal deformity.

EXAMPLE 5

A segment of the device for the correction of spinal deformitiesaccording to the Example 4 but differentiated for it contains (see theFIG. 6) the spring 4 fixed on the body of the segment 2 which is notstraight-lined, but which is shaped along its entire length in such amanner that, at also limited opportunities for changing its positionregarding the body 2 of the segment, it is possible to reach, due to itscurvature, a required force acting on the next vertebra.

EXAMPLE 6

A segment of the device for the correction of spinal deformitiesaccording to the Example 5 but differentiated in such a way that in theprominence 9 a through aperture 16 is formed (see the FIG. 7) in which ahollow screw 8.1 ok is located. The mentioned hollow screw 8.1 isequipped on its external surface with a thread and it has in itsinterior an aperture 10 with a thread, while one end screwed in thevertebra 7 is divided by longitudinal cuts on at least two parts. In theaperture 10 with the thread the fixation screw 8 is located which whenbeing screwed into the aperture 10 having the thread spreads separatelongitudinal parts of the hollow screw 8.1 and thus increases thestrength of its fixation in the vertebra 7.

The above-mentioned examples of the device for the correction of spinaldeformities according to the invention represents wanly illustrativelyconcrete executions which in any case do not restrict the extent of theinvention defined in patent claims.

INDUSTRIAL APPLICABILITY

The device according to the invention may be appropriately applied, dueto its constructive modification, to all known spinal deformities.

We claim:
 1. The device for the correction of spinal deformities, comprising:at least two segments adapted for affixation on spinal vertebrae and which are mutually interconnected; each segment (1) comprising a body (2) of the segment equipped with at least one fixing element (3) adapted for affixation on at least one spinal vertebra (7) and with at least one spring (4), by means of which a first segment is connected by force coupling with at least one other segment (1'); and the spring (4) having ends disposed on a connecting line that forms a 45° angle with the vertical vertebral axis (7) in the frontal plane and a 45° angle in the sagittal plane in either the ventral or dorsal direction.
 2. The device according to claim (1), wherein a first end of the spring (4) is firmly connected with one segment (1) and a second end of the spring is firmly connected with the other segment (1').
 3. The device according to claim 1, wherein a first end of the spring (4) is firmly fixed on one segment (1) and a second segment (1') is equipped with a bearing case (5) in the form of an aperture in the body (2') of the segment in which the second end of the spring (4) is received, and the cross dimensions of the aperture are greater by at least 0.01 mm than the corresponding dimensions of the second end of the spring (4).
 4. The device according to claim 3, wherein each segment (1, 1') contains at least one spring (4) and one bearing case (5).
 5. The device according to claim 1 wherein the segments (1) are adapted for being applied on different places of a spinal deformity, and the springs (4) differ from each other in at least one of their dimensions or the material they are made of or in the shape or the angle which they form with the vertical vertebral axis (7).
 6. The device according to claim 3, wherein:on the segment body (2) a prominence (9) is formed having the shape of a globular section in which near its top a threaded aperture (10) is located; an end (11) of the spring (4) has a form of a hollow globe section of an internal diameter, substantially equal to the prominence (9) radius but of height smaller by at least 0.01 mm; a through circular aperture (12) is formed near the top of the globe section so the segment (1) contains a fixation washer (13) with an excavation (14) having the form of a globular section of a diameter substantially equal to the external radius of the end (11) of the spring (4); a through aperture (15) is formed near the top of the excavation (14); the end (11) of the spring (4) is by its concave side of the hollow globe section disposed on the prominence (9); the convex side of the hollow globe section is disposed on the excavation (14) of the fixation washer (13); and the mutual position of these elements is fixed by a screw (8) having a diameter less by at least 0.01 mm than the diameter of the apertures (12, 15) through which the screw passes and is screwed in the threaded aperture (10).
 7. The device according to claim 6, wherein:in the prominence (9) of the globular section form, near its top, is created a through aperture (16) and in the through aperture a hollow screw (8') is placed, which contains a threaded aperture (10) and which is adapted to be screwed through a pedicle into a spinal vertebra (7) body.
 8. The device according to claim 6, wherein the segment (1) contains the bearing case (5) in the form of an excavation formed in the segment body (2) with one side open and covered by the fixation washer (13).
 9. The device according to claim 8, wherein the spring (4) contains at its free end at least on a part of the circumference enlargement (16), and a groove (17) is formed at the end of the bearing case (5) of the second segment (1') which is more removed from the first segment (1), on which the spring (4) is fixed.
 10. The device according to claim 1, wherein the fixing element (3) is a shaped clamp equipped at the ends of arms with a tightening screw (6), and the internal aperture of the fixing element (3) has a form of a cross cut of the vertebral arch (7) in a place between the spinous processus and the pedicle of the vetebra (7). 